Mobile loaders are essential equipment for the loading and unloading of containerized or palletized cargo into and from the holds of aircraft. Such loaders often employ two platforms. One platform, usually referred to as the bridge, provides an interface with the sill of the cargo door of the aircraft. The bridge is supported on a hydraulic lift, which provides a high degree of control and stability and allows the height of the bridge to be adjusted to correspond to the height of the aircraft cargo door. Once the bridge is positioned, it typically remains in a substantially constant position with respect to the aircraft, although it is known to make slight adjustments to the height of the bridge to compensate for shifts in the height of the aircraft cargo door as the plane is loaded or unloaded. Although the following discussion is presented in terms of a loading process, in which cargo is placed onto an aircraft, it will be understood all concepts apply equally to unloading processes.
The second platform, hereinafter referred to as the platform, onto which cargo may be loaded by means of a truck to one side, cycles up and down during the loading process to deliver cargo to the bridge. The platform is typically raised and lowered by means of hydraulic systems acting through appropriate mechanical linkages which ensure that the platform maintains a substantially horizontal attitude. For example, a pair of chains powered by hydraulic cylinders cooperate with a platform squaring or stabilizing scissors to ensure that the platform moves vertically during raising and lowering. Cargo loaders of this type are known in the art. As used herein, objects on which cargo is loaded includes both closed containers with relatively rigid bases and pallets having relatively flexible bases with loads of the cargo secured thereto.
The decks of the platform and bridge sections of cargo loaders are typically provided with some combinations of retractable guide rails that function to prevent movement of the cargo in an undesired direction. In addition, because the control panel for the loader is typically positioned on the bridge, since it is often necessary for the operator to walk about on the bridge, and because the bridge is typically several feet above the ground, the bridges of cargo loaders are usually supplied with a handrail which spans the port side of the bridge, as the forward edge of the bridge contacts the aircraft with its rear edge contacting the platform, and its starboard side being enclosed by the control cage or railing.
However, the configuration of aircraft and the maneuverability of the loaders makes it necessary to remove or lower the port handrail from time to time, so as to allow the loader to approach the aircraft and/or clear the aircraft or other equipment. In some prior loaders, the handrail is completely detachable from the bridge and therefore often becomes separated from the loader, gets lost and can no longer serve its intended purpose. In other prior loaders, the handrail is pivotally mounted on the bridge, and is secured in its upright position by a drop-in type of engagement with a receiving channel on the bridge frame. In either case, the operator is required to manually lift the entire weight of the handrail, both to engage and disengage it from the bridge. Aside from the hazards associated with heavy lifting, this is particularly dangerous, as secure footing on the bridge is hampered by the presence of friction reducing devices on the bridge deck.
Hence it is desired to provide a platform having such a handrail which is quickrelease, and quick-engaging and lift-assisted as it is moved between upright and inclined positions on the platform.